As a known substrate used as an interposer (hereinafter also referred to as “interposer substrate”), there is an insulating base material having multiple linear conductors penetrating the insulating base material in a thickness direction of the insulating base material. Each linear conductor has one end exposed in one surface of the insulating base material and another end exposed in the other surface of the insulating base material. In the interposer substrate, pads are formed opposing each other on the one and the other surfaces of the insulating base material. The pads formed on the one and the other surfaces of the insulating base material are electrically connected to each other by way of the linear conductor. This interposer substrate may have a semiconductor chip mounted thereon (see, for example, Japanese Laid-Open Patent Publication No. 2010-272562).
As described above, the interposer substrate has pads formed opposite to each other, on the one and the other surfaces of the insulating base material. However, in reality, it is difficult to form pads positioned exactly opposite to each other on the one and the other surfaces of the insulating base material due to inconsistent manufacturing. Accordingly, it becomes necessary to take position deviation between the pads into consideration when designing the interposer substrate. Thus, the narrowing of the pitch between the pads becomes limited.
Accordingly, as the narrowing of the pitch between the electrode pads of a semiconductor chip progresses, it becomes difficult to mount the semiconductor chip on the interposer substrate.